6 months 'no questions asked' guarantee...
"If Cockroaches appear after we treat your home, I will personally re-treat your home and write you a check for $200."
Roger's Bug Treatment Service
After this, the copy details the guarantee and there can be pictures of checks, etc.
I used this for an Australian Internet marketer and it got a 50 per cent better result than the control.
I'm a direct response copywriter with repeat clients around the world. My website is here.